Sideband mitigation communication systems and methods for increasing communication speeds, spectral efficiency and enabling other benefits

ABSTRACT

Common wave and sideband mitigation communication systems and methods are provided that can be used with both wireless and wired communication links. The systems and methods provided can enable faster data rates, greater immunity to noise, increased bandwidth/spectrum efficiency and/or other benefits. Applications include but are not limited to: cell phones, smartphones (e.g., iPhone, BlackBerry, etc.), wireless Internet, local area networks (e.g., WiFi type applications), wide area networks (e.g., WiMAX type applications), personal digital assistants, computers, Internet service providers and communications satellites.

PRIORITY CLAIM/RELATED APPLICATION

This application is a divisional of and claims priority under 35 USC§§120 and 121 to U.S. Provisional Patent Application Ser. No.12/839,300, filed on Jul. 19, 2010 and entitled “Common Wave AndSideband Mitigation Communication Systems And Methods For IncreasingCommunication Speeds, Spectral Efficiency And Enabling Other Benefits”which in turns claims the benefit and priority under 35 USC 119 and 120to PCT Application Serial No. US2008/087812, filed on Dec. 19, 2008 andentitled “Common Wave And Sideband Mitigation Communication Systems AndMethods . . . Other Benefits” which in turn claims the benefit under 35USC 119(e) and priority to under 35 USC 120 of U.S. Provisional PatentApplication Ser. No. 61/015,043 filed on Dec. 19, 2007 and entitled“Common Wave Communication System and Method for IncreasingCommunication Speeds and/or Enabling Other Benefits”, the entirety ofwhich is incorporated herein by reference.

FIELD

A wired or wireless communication system and method are provided.

BACKGROUND

Various wired and wireless communication systems are well known. Forexample, as shown in FIGS. 1 and 2, two different conventionalcommunication systems are known. As shown in FIG. 1, one example of aconventional wired communication system has a transmitter and receiverwherein a data signal is communicated over a first wired communicationslink and a second data signal (which is an inverted form of the datasignal) is communicated over a second wired communications link. In thesystem shown in FIG. 1, the two wired communications links are nearbyeach other. The receiver may receive these two data signals and thentake the difference between the two data signals in order to extract thedata from the data signal. This conventional communication system isknown as a differential signal system that allows lower voltages to beused since only the difference between the two signals is needed, allowshigher data transmission speeds and increases noise immunity since anynoise would affect both the communication links and the noise would befiltered out when the difference between the two data signals isdetermined. The system shown in FIG. 1 may be used, for example, on aprinted circuit board in which each wired communication link is a traceon the printed circuit board.

An example of how the system in FIG. 1 works on copper wires is that thetwo adjacent wires each have a signal in which one is the inverse of theother. For example, if a “digital 1” is to be transmitted with 1 voltlevels, Line A will be at 1 volt and Line B will be at 0 volt (i.e., theinverse) while a “digital 0” is transmitted with Line A at 0 volts andLine B at 1 volt. As the wires run from the transmitter to the receiver,the wires might both pickup noise which will cause the voltage levels inthe lines to be raised or lower in addition to causing spikes which canappear to be data. If the 2 wires are in very close physical proximityto each other, the noise will be identical in both wires. At thereceiver end, the 2 lines will be connected to a differential amplifiercircuit. This differential amplifier circuit will “subtract out” thenoise.

FIG. 2 illustrates an example of another conventional communicationsystem that may be a wireless communication system. In thiscommunication system, a transmitter may generate and communicate aplurality of data signals over a communication link and then thereceiver extracts data from each data signal independently, but there isno relationship between the data signals that aids in the extraction ofthe data from the data signals. The system shown in FIG. 2 may be usedfor a typical mobile phone system such as a time division multiplex or acode division multiplex communication system.

FIG. 3 illustrates a wireless communications system that uses a pilotsignal wherein the pilot signal is modulated with the carrier wave anddata signal to generate a single output signal that is then sent over acommunications link to a receiver. The receiver then uses the pilotsignal (embedded in the output signal) to decode the data signal. Inthis conventional system with a pilot signal, only a single signal issent over the communications link.

None of these conventional communication systems use a data signal and areference signal (transmitted over the same communications link but ondifferent channels) and thus it is desirable to provide a common wavesystem and method and it is to this end that the system and method aredirected.

In addition, it is desirable to provide systems and methods forminimizing effective bandwidth and neutralizing sidebands (sidebandmitigation) that enable substantial increases in data transmission speedand spectral efficiency and it is to this end that the system and methodare also directed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 2 illustrate conventional communication systems;

FIG. 3 illustrates a conventional pilot signal communication system;

FIG. 4 illustrates an implementation of a common wave communicationsystem having a transmitter and receiver;

FIG. 5 illustrates more details of an example of the common wavecommunication system shown in FIG. 4;

FIG. 6 illustrates an example of an implementation of the common wavecommunication system shown in FIG. 4;

FIG. 7 illustrates an example of expected signals for a demodulatorcircuit in a common wave communications system receiver to compare tothe input signal;

FIG. 8 illustrates an example of a method for common wave communication;

FIG. 9 illustrates an example of a method for resetting a data signal ofthe common wave communication system;

FIGS. 10 and 11 illustrate an example of a method for minimizingeffective bandwidth of a communication system;

FIG. 12 illustrates an example of a filter for use with signals thathave alternating phases;

FIGS. 13 and 14 illustrate an example of a method for neutralizingsidebands of a communication system;

FIG. 15 illustrates an example of a circuit for generating 1 GHz carrierwave with a 1.414V amplitude & 0° phase;

FIG. 16 illustrates an example of a time domain for the 1 GHz carrierwave unmodulated;

FIG. 17 illustrates an example of a FFT of the 1 GHz unmodulated signalfor 1000 ns;

FIG. 18 illustrates an example of a FFT for 1 GHz unmodulated signal for1000 ns sample with 250 kHz-20 dB mask;

FIG. 19 illustrates an example of a circuit with data signal generatedby V2 and modulation done by Phase_Modulator_(—)90_deg;

FIG. 20 illustrates an example of a data signal for the first 124 ns.Data bit period is 8 ns;

FIG. 21 illustrates an example of a modulated signal. Data bit 1 isphase 90°. Data bit 0 is phase 0°. 34 ns shown;

FIG. 22 illustrates an example of an FFT of the 125 Mbps, 90° phaseshift, modulated signal;

FIG. 23 illustrates an example of an implementation of a first step inSideband Mitigation circuitry;

FIG. 24 illustrates an example of a modulated signal has data bit 1start with phase 0 and data bit 0 start with phase 180;

FIG. 25 illustrates an example of an FFT with 1 GHz lobe removed.Sidebands are worse;

FIG. 26 illustrates the 867 MHz and 884 MHz lobes shown with phase;

FIG. 27 illustrates an example of an implementation of a SidebandMitigating signal added to reduce a 867 MHz lobe;

FIG. 28 illustrates an example of a 867 MHz lobe minimized but residuallobes remain;

FIG. 29 illustrates an example of an implementation of a 868 MHzresidual lobe that has been mitigated;

FIG. 30 illustrates an example of an implementation of a signal with allthe sidebands below 1 GHz mitigated;

FIG. 31 illustrates an example of an implementation of an FFT withsidebands below 1 GHz mitigated with Sideband Mitigation signals shownin Table 1; and

FIG. 32 illustrates an example of a circuit for phase filtering.

DETAILED DESCRIPTION OF ONE OR MORE EMBODIMENTS

The system and method are particularly applicable to a wirelesscommunication system with a single communications link using a discretehardware circuit based transmitter and receiver as described below andit is in this context that the system and method will be described. Itwill be appreciated, however, that the system and method has greaterutility since the system and method may be used with wired (for example,a fiber optic, wires, a printed circuit board (PCB) trace, etc.) orwireless communication systems (for example, cellular phone systems,mobile device wireless systems, etc.), may be implemented as atransmitter or a receiver only, and/or may be implemented in software(soft transmitter and/or receiver), hardware (as shown below or otherimplementations) or a combination of software and hardware (for examplea digital signal processor with firmware or other implementations).

In the context of this disclosure, “mobile device” may include anymobile wireless communications device including but not limited to: acellular phone, Personal Communications Service PCS, smartphone (e.g.,iPhone, BlackBerry, etc.), wireless internet cards or circuits forcomputers, wireless local and wide area network (e.g., WiFi, WiMax,etc.) cards or circuits, satellite phones, GPS tracking devices, etc.The device using the common wave system and method is mobile deviceregardless of the type of data the device is transmitting or receiving.For example, the data being transmitted or received may include any typeof information including but not limited to voice, data files, video,broadcasts, music, telemetry, radio, etc.

FIG. 4 illustrates an implementation of a common wave communicationsystem 400 having a transmitter 401 and a receiver 402. Thecommunication system 400 may also include a communication link 403 thatmay be a medium over which a signal can be transmitted between thetransmitter and the receiver. The medium may include the atmosphere,space, water, wire, coaxial cable, fiber optics, printed circuit boardtraces, integrated circuit traces, drilling mud, AC power distributionlines, etc. In the communication system, there may be a plurality ofchannels 406 in the communication link 403. The communication system mayinclude at least one data channel 404 that contains a data signal, atleast one reference channel 405 that contains a reference signal and oneor more other channels 407 that can contain data or reference signals.The communication link for the at least one data channel and thecommunication link for the at least one reference channel may be thesame communication link or may be different communication links.

In the common wave system, the data signal may be known as a data wavewhich has an information signal modulated onto a carrier wave usingvarious modulation techniques, such as for example frequency modulation,amplitude modulation, phase modulation, or a combination thereof, etc.The reference signal may be known as a common wave that may be a knownfrequency signal (that may be fixed or adjustable in a known manner)that acts as a reference wave to the data wave. In one embodiment, thedata wave and the common wave may be at different frequencies but thedifferent frequencies are close to each other. In one embodiment, suchas code division multiple access (CDMA) mobile phone system that employsfrequency hopping, although the data wave and the common wave are atdifferent frequencies at any one instant in time, the data wave may beat the same frequency as the common wave was at some other instant intime due to the frequency hopping. In another embodiment, the commonwave signal may be transmitted for a predetermined number of cycles at aparticular frequency and then the data wave signal may be transmittedfor a predetermined number of cycles (different from the predeterminednumber of cycles during which the common wave signal is transmitted) atthe same frequency or at a different frequency. In another embodiment,the data wave signal and the common wave signal may be at the samefrequency wherein a series of common wave signals are transmitted andthen a series of data wave signals are transmitted (or a series of datawave signals are transmitted and then a series of common wave signalsare transmitted) wherein the common wave signals can be used tocalibrate the receiver and provide some noise filtering for the datawave signals.

In one embodiment of the common wave system, the one or more datasignals 404 and the one or more reference signals 405 are simultaneouslycommunicated over the communications link 403 and received by thereceiver 402. In other embodiments, the one or more data signals and theone or more reference signals are not simultaneously communicated overthe communications link. When the one or more data signals and the oneor more reference signals are received by the receiver 402, each datasignal is compared to a corresponding reference signal in order toextract an information signal from the data signal. The common wavesystem provides increased noise immunity because the data signals andthe corresponding reference signal will both be affected in a similarmanner by noise in the communication link 403 so that the comparison ofthe data signal to the reference signal in the receiver filters out aportion of the noise, reduces the noise level in the data signal whichresults in a better signal to noise ratio and thus a higher possibletransmission rate as is well known due to Shannon's Law.

FIG. 5 illustrates more details of an example of the common wavecommunication system 400 shown in FIG. 4 in which a single data signalchannel and a single reference signal channel are shown beingcommunicated over a wireless communication link for illustrationpurposes. As above, the data signal 404 and the reference signal 405 arecommunicated over the communications link 403 between the transmitter401 and the receiver 402. The transmitter 401 may have a modulator 503that modulates an information signal 502 onto a carrier wave 501 (with aspecific frequency) to generate the data signal. In one embodiment, aphase modulator circuit may be used. A common wave signal 405 isgenerated, but is not (in the example shown in FIG. 5) modulated beforeit is transmitted. The data signal and the common wave signal are thentransmitted via one or more antennas 505 over the communication link 403to the receiver 402.

The receiver 402 may receive the signals from the communication linkusing one or more antennas 506 wherein the signals received by theantennas 506 that input into a first filter 507 and a second filter 508wherein the first filter is tuned to the frequency of the carrier waveof the data signal and the second filter is tuned to the frequency ofthe reference signal. Thus, the first filter allows the data signal tobe output (and filters out other signals) to a first input of a signalcomparison device 509 while the second filter allows the referencesignals to be output (and filters out other signals) to a second inputof the signal comparison device 509. In one embodiment, the signalcomparison device may be a differential amplifier that compares thesignals at the first and second inputs. Thus, the signal comparisondevice 509 outputs a signal that is the difference between the datasignal and the reference signal, which removes noise introduced in thecommunication link 403. The output of the signal comparison device isfed into a demodulator 510 (such as a phase demodulator in the examplein FIG. 5) that also receives a replica of the carrier wave (generatedlocally in the receiver or extracted from the transmitted signals) inorder to generate an information signal 511 that corresponds to theinformation signal 502 input to the transmitter 401. In one embodimentusing a differential amplifier, the output of the differential amplifiercan then be analyzed to identify the data (demodulated). While thissignal will be significantly different than normal wireless signals tobe demodulated, it can be analyzed with well-known techniques usingstandard circuitry or digital signal processors (DSP).

FIG. 6 illustrates an example of an implementation of the common wavecommunication system shown in FIG. 4. In this implementation, thetransmitter 401 may further comprise a carrier wave generator 601, suchas for example a voltage controller oscillator, that generates thecarrier wave such as a carrier wave at 910.546 MHz and a reference wavegenerator 602, such as for example a voltage controller oscillator, thatgenerates the reference wave such as a reference wave at 925.000 MHz. Inthis implementation, the modulator 503 may be a phase shifter circuitthat shifts the carrier wave phase based on the information signal 502.In this implementation, the data signal and the reference wave are inputinto a signal amplifier 603, such as a radio frequency amplifier, thatboosts the strength of both signals before they are radiated by the oneor more antennas 505.

The receiver 402 in this implementation may further include an amplifier604, such as a low noise amplifier, that boosts the signal strength ofthe received signals (both the data signal and the reference signal),which are then fed into the filters 605, 606 whose outputs are then fedinto a differential amplifier 607 whose output is fed into thedemodulator 510. In this implementation, the demodulator 510 may be acircuit (such as a thresholding circuit) that compares the incominginformation signal (output from the signal comparison devicedifferential amplifier 607) to an expected signal for a “1” or a “0” andoutputs the recovered information signal. The expected signals for a “1”and a “0” for one embodiment in which the “1” starts positive 90 degreesout of phase with the data wave and the “0” starts negative 90 degreesout of phase with the data wave.

FIG. 8 illustrates an example of a method 800 for common wavecommunication that may be carried out by the transmitter and receivershown in FIGS. 4-6 above. At the transmitter, the system selects arelationship between the data signal and the reference signal (801)which may be communicated to the receiver in some fashion (e.g., therelationship may be preconfigured or set during each communicationsession). The relation ship may be specific differences in amplitudes,frequencies, phases and/or polarities at specific points in time. In oneembodiment, the system can have a default setting (set at both thetransmitter and receiver) and then can adjust the relationship as neededby communicating with each other. An example of the default relationshipmay be a typical amplitude, frequency and/or phase modulation and thechanging of the relationship during the communications may be done toprovide frequency hopping and/or adjusting signal strength. Once therelationship is determined, the transmitter may create a referencesignal and a data signal (802) based on an information signal (803).Once the signals are generated in the transmitter, the data signal iscommunicated over a data signal channel (804) and the reference signalis communicated over a reference signal channel (805) over one or morecommunications link(s) 403. The receiver then receives the transmittersignals (806) and then uses the relationship information to extract theinformation signal from the data signal in the data channel (807) sothat the information signal is outputted (808).

FIG. 9 illustrates an example of a method for resetting a data signal ofthe common wave communication system. When the reference signal and thedata signal are simultaneously transmitted, the two signals becomesuperimposed which may cause significant destructive interference formuch of the time (about 50% of the time) which is common to manywireless systems. To overcome this superimposition issue, in oneembodiment of the common wave communication system using phasemodulation, the transmitter may periodically reset the data signal tobring it back into phase with the data signal as shown in FIG. 9. In oneembodiment, the data wave may be reset every 4 signal periods (such asshown in FIG. 9). In addition to the phase modulation embodiment, theresetting of the data signal may also be used for amplitude modulationembodiments, frequency modulation embodiments and other modulationembodiments. In addition to the common wave communication system withthe data signal and reference signal simultaneously transmitted, theresetting of the data signal may also be used with systems that do notsimultaneously transmit a data signal and a reference signal.

Controlling Effective Radiated Power

As described above, the common wave system may transmit the common waveat a fixed frequency and the signal is essentially unmodulated and thedata channels with the data signals are at different frequencies and theamplitude of the data channel signals have a known relationship to thecommon wave signals. In one embodiment, the common wave signal amplitudemay be significantly higher than the data signals, such as 0-20 dB.Then, at the receiver, a very narrow band pass filter (BPF) detects thecommon wave signal.

The significantly higher amplitude common wave signal establishes, atthe receiver, a strong reference signal for evaluating the frequency,phase, amplitude and/or time of the data signals. The strong referencesignal may be used by hardware, software, a digital signal processor(DSP), etc. to differentiate the data signal from noise anddecoding/recovering the data signals.

As an example, the common wave signal may be transmitted at an effectiveradiated power (ERP) of 100 watts and there may be eight data channelseach transmitting at an ERP of 50 W to 8 different receivers. For thecommon wave signal, the receiver may have a band pass filter with abandwidth of 100 kHz so that the receiver will be receiving a strongsignal that is being sampled over a 10 microsecond period. It is wellknown that a 100 W signal is better able to penetrate walls and weatherand deal with noise, multipath and travel speeds than a 50 W signal.Therefore, each of the eight receivers will receive a strong common wavesignal which will be used as a reference for evaluation the specificsignal that is of interest to the specific receiver.

In most actual implementations of communication systems, there arelimits on the amount of power each transmitter is allowed to transmit.For example, in general in the United States, mobile phone towertransmitters are only allowed to transmit 500 W ERP so that one cannotdesign an implementation of a communication system with eight 100 W datasignals because the transmitter would exceed the maximum power allowed.However, an implementation that has a powerful common wave signal and aplurality of data wave signals at lesser power allow the communicationsystem to meet the transmission maximum power levels while allowing thedata signals to be more accurately decoded/recovered due to the strongerpower common wave signal. The above higher power common wave signal maybe broadcast to a large number of receivers that can each utilize thecommon wave signal so that the ratio of the common wave signal to thenumber of data wave signals may be 1 to 8 (the above example), 1 to 100,1 to 1000 or 1 to 1,000,000. In fact, there is no limit to the number ofdata channels that can use a single common wave signal. The advantage ofmore data channels using the same common wave signal is that the commonwave signal takes up a smaller percentage of the total allowable ERP. Inone embodiment, multiple mobile phone service providers using the samecell tower could use the same common wave signal thereby allowing all ofthem to increase the ERP to each data channel.

Minimizing Effective Bandwidth

FIGS. 10 and 11 illustrate an example of a method for minimizingeffective bandwidth of a communication system. The method illustrated inFIGS. 10-11 may be used with conventional communication systems as wellas the common wave communication system.

In an exemplary communication system, if a carrier frequency is 1 GHz,and digital data is modulated via AM, FM or PM at 10 MHz, the frequencyband that will be transmitted is from 990 MHz to 1.010 GHz which causesinterference problems with 995 MHz if it needs to be used as atransmission channel. The resulting increase in bandwidth is one of manyfactors that limit the total amount of data that can be transmitted in agiven frequency band. To overcome this interference at 995 MHz andminimize the bandwidth of the carrier wave, the communication system mayuse a carrier wave that is phase shifted 180 degrees at predeterminedtimes as shown in FIG. 10. For simplicity, the information signal thatis modulated onto the carrier wave is not shown. As shown in FIG. 11,this phase shifting makes the average power at the carrier frequency andthe nearby channels, e.g., 995 MHz, zero. This allows 995 MHz to be usedas a communications channel using the common wave system or conventionaltechnologies and be unaffected by the 1 GHz channel.

In one embodiment, if the transmission signal is phase shifted every 10cycles, the receiver must also be “phase shifted” to be able to handlethe incoming signal. If adjacent channels also use this phase shiftingapproach, the timing for each channel's phase shifting can be offsetfrom the other channels. This will enable more channels to be crammedinto the same frequency band without inter-channel interference.

In traditional filters for transmitters or receivers, alternating thephase of a signal as shown in FIG. 10 can prevent the circuit fromresonating effectively and hence the circuit will output a weak signal.FIG. 12 shows an embodiment of an alternating phase signal filter 1200which effectively reaches resonance for a signal with an alternatingphase. A switch 1201 alternates positions based on the switch controlinput. The timing of the position switch is such that the conventionalbandpass filter or resonant circuit 1202 always has the same phase inputto it. This allows the circuit to achieve resonance and thus pass astrong signal at the desired frequency and phase. Also, this will causedestructive interference for frequencies and phases that are notdesired. This same type alternating phase signal filter 1200 will workwell with signals that have been reset as shown in FIG. 9.

In the embodiment shown in FIG. 10, the carrier wave is phase shifted180 degrees but it can be appreciated that other combinations of phaseshifting can achieve the similar results and the system is not limitedto the 180 degree phase shift shown in FIG. 10. For example: 10 carrierwaves at 0 degrees, 10 carrier waves at 120 degrees and 10 carrier wavesat −120 degrees will have a lower average power at the carrier frequencythan 30 waves at 0 degrees. Also, combinations of different phases,amplitudes and frequencies can have similar effects and are within thescope of this disclosure.

Neutralizing Sidebands

FIGS. 13 and 14 illustrate an example of a method for neutralizingsidebands of a communication system. The method illustrated in FIGS.13-14 may be used with conventional communication systems as well as thecommon wave communication system. When a wireless signal is changed(amplitude, frequency and/or phase) the bandwidth is increased andsidebands are created. The sidebands are a necessary part of wirelesscommunication in many protocols, e.g., “single sideband.” In manycircumstances though, sidebands are an undesirable byproduct of thesignal modulation.

As shown in FIG. 11, significant sidebands are seen which are generatedby the phase shifting of the carrier signal. These are undesirablebecause they will be radiated and cause interference with other channelsat those frequencies. The traditional method of eliminating sidebands isthe use of low pass, high pass or bandpass filters. These traditionalfilters are undesirable in a situation where high speed data signals areinvolved because the filters degrade the high speed signals. In theneutralizing sideband method that may be used with the common wavesystem, a “neutralizing signal” may be injected into the transmissionline along with the carrier signal. As shown in FIG. 13, to neutralizethe 950 MHz sideband, a 950 MHz signal with a specific predeterminedamplitude and phase are used to neutralize that sideband and FIG. 13shows that the resultant signal where the 950 MHz sideband isneutralized. For example, the injected signal needs to be the sameamplitude and 180 degrees phase shifted from the sideband to beneutralized. In the example shown in FIG. 13, the carrier wave has anamplitude of 1 volt (see FIG. 10) and the injected 950 MHz signal has anamplitude of 0.6525 volt. The injected signal starts out of phase withthe carrier wave 90 degrees. In addition, additional signals can besimilarly injected to eliminate other side bands.

The injection of a signal into the transmission line can be used toeliminate sidebands created from all sources of sidebands as long as theamplitude, frequency and phase of the sideband is known in advance.These values can be determined from previous transmissions in alaboratory environment and then be used in a field setting. Even in thecase of sidebands created from data modulation, an appropriate sidebandneutralizing signal can be injected into the transmission line. Thespecifics of that neutralizing signal will be different depending on thevalue of the data.

At the receiver end of the transmission system, the original carrierwave is recovered using known techniques. In the case of the injectedneutralizing signals, those injected neutralizing signals are removed torecover the original carrier wave.

In the context of the disclosure, “transmission line” is defined as anypath used to transfer the signal energy from one location to another.This includes but is not limited to: conductors in the transmitter,waveguides, lines connecting the transmitter to the one or moreantennae, amplifiers or communications links, including wirelesscommunications links.

Now, a detailed example of the above neutralization of sidebands(sideband mitigation) is described in which simulations are used toillustrate the neutralization of sidebands. The example presented belowillustrates how the neutralization of sidebands can substantiallyincrease the spectral efficiency of wireless communication. In theexample, well known signals will be shown as a starting point and thensignals utilizing the described sideband mitigation will be shown forcomparison. For purposes of the example, a carrier wave of 1 GHz is usedalthough the disclosed sideband mitigation can be used with anyfrequency and thus is not limited to any particular frequency. Thisexemplary frequency is used because it is in close proximity to commonfrequency bands such as cellular phones (800, 900, 1800, 2100 MHz), WiFi(2.4 GHz) and WiMax (2.3, 2.5 and 3.5 GHz). For purposes of the example,the simulation software used is LTspice/SwitcherCAD III Version 2.24iproduced by Linear Technology Corporation.

A circuit that can create the 1 GHz carrier wave for this example isshown in FIG. 15. The voltage source generates a sine wave with a 1.414V amplitude and 1 GHz frequency. Simulating this circuit in the timedomain provides voltage vs. time oscilloscope output as shown in FIG.16. Performing a well known FFT (Fast Fourier Transform) simulation onthe signal voltage results in FIG. 17. For purposes of this example, allFFT operations are performed for a 1000 ns time period using a Hammingwindowing function, 1,048,576 data point samples, and 5 point binomialsmoothing unless specified otherwise.

To demonstrate how Federal Communications Commissions (FCC) regulationsare applied, let us look at CFR Title 47, Part 15—Radio FrequencyDevices, §15.247 Operation within the bands 902-928 MHz, 2400-2483.5MHz, and 5725-5850 MHz which provides:

-   -   §15.247 Operation within the bands 902-928 MHz, 2400-2483.5 MHz,        and 5725-5850 MHz.    -   (a) Operation under the provisions of this Section is limited to        frequency hopping and digitally modulated intentional radiators        that comply with the following provisions:    -   (1) Frequency hopping systems shall have hopping channel carrier        frequencies separated by a minimum of 25 kHz or the 20 dB        bandwidth of the hopping channel, whichever is greater . . . .

The power for the carrier wave shown above is 20 mW which is below themaximum levels for those bands and 1 GHz. Zooming in on the FFT resultsand drawing the 250 kHz (20 dB) bandwidth mask results in FIG. 18 inwhich the signal does not fit within the mask because the FFT is onlysampling for 1000 ns.

To add data to the carrier wave, a data signal is generated by V2 andoutput to TP_Data in FIG. 19. The following data for the example isarbitrarily selected:

10110011 10001111 00001111 10000011 11110000 00111111 10000000 1111111100000000 11111111 10000000 00111111 11110000 00000011 11111111 10000000

The data rate is 125 Mbps which is a period of 8 ns. The first 124 ns ofthe signal is seen in FIG. 20.

The Phase_Modulator_(—)90_degree shown in FIG. 19 modulates the carrierwave with the data wave wherein a data bit “1” is phase shifted 90° anda data bit “0” is phase shifted 0°. FIG. 21 shows the first 36 ns of themodulated signal. FIG. 22 shows the FFT of the modulated signal that hassignificant sidebands. As expected, the lobes do not fit within the maskbecause the data rate is too high. As seen, the 20 dB bandwidth is 22MHz as shown in FIG. 22.

The sideband mitigation system disclosed herein provides increasedspectral efficiency which is defined as:(Spectral Efficiency)=(Data Rate)/(Bandwidth)  (Equation 1)

Using Equation 1, we find the spectral efficiency for the signal shownin FIG. 21 is:SE_(−20 dB)=(125 Mbps)/(22 MHz)=5.7 Mbps/MHz

Any attempt to use a bandpass filter (a typical solution) to improve thespectral efficiency of the signal of FIG. 21 will not be useful becausethe bandpass filter will filter out the data. However, the spectralefficiency can be improved using known techniques which include the useof: reducing the delta phase shift below 90° (e.g., 11.5°), amplitudemodulation, and others. These known techniques work and are usedregularly but have limitations due to real world noise and sensitivityof the hardware. For example, reducing the delta phase shift 11.5° willmake the receiver more susceptible to phase noise (jitter) andapproaches the limits of the resolution of phase detector. Thus, thetypical solutions have limitations and/or do not provide sufficientresults. The sideband mitigation technique disclosed herein improvesover these known techniques and in fact can be used with these knowntechniques to reduce sidebands and increase spectral efficiency.

To implement the disclosed sideband mitigation, the center lobe shown inFIG. 22 may be examined. As shown in FIG. 23, a 250 MHz clock may beadded with output TP_CLK_(—)250 and the a phase shift modulator withoutput TP_FN1. Due to the Phase Shift Modulator, each data bit is phaseshift 0 for half the data period and phase shift 180 for the other half.If the data bit is a 1, it is phase 0 for the first half and phase 180for the second half. If the data bit is a 0, it is phase 180 for thefirst half and phase 0 for the second half as shown in FIG. 24. InLTspice (the simulation software used in the example), “^” (shown inFIG. 23 is an operand that “Convert(s) the expressions to either side toBoolean, then XORs (exclusive ors) the result.

The modulation of the sideband mitigation technique causes each data bitto cancel itself out on the FFT which results in the 1 GHz lobe beingeliminated as seen in FIG. 25, but the other lobes in FIG. 22 are worsethan before. Zooming in on 867 MHz in FIG. 25 and adding phase givesFIG. 26 in which the lobe is centered at 867 MHz, the peak is at −11.7dB and the phase is −24° (and 1 GHz is at −7°.) To mitigate the 867 MHzlobe, we add a 867 MHz, 0.368 V amplitude, 245° phase sine wave,V(TP_FN2) to the signal. The results are TP_FN2 and shown in FIGS. 27and 28.

FIG. 28 shows residual lobes remain from the first mitigation attempt.To mitigate the 868 MHz lobe, add a 868.6 MHz lobe w/0.200 amplitude and250° phase. These results are shown in FIG. 29. These steps can berepeated for elimination of all the lobes above the −20 dB mask therebyenabling a 125 Mbps data rate to fit within a 250 kHz bandwidth FCCallocation. Using this number in Equation 1, the spectral efficiency ofthe sideband mitigation system is:SE_(−20 dB)=(125 Mbps)/(250 kHz)=500 Mbps/MHz

That is substantially higher the spectral efficiencies of existingtechnologies. It could be stated that actual spectral efficiency per thestandard equation is infinity. The elimination of all the lobes below 1GHz is achieved with the SBM signals shown in Table 1 below and theresultant signal is shown in FIG. 30 and the FFT shown in FIG. 31.

TABLE 1 Frequency Amplitude Amplitude Phase Phase (MHz) (dB) (V)(degrees) (radians) 867 −11.7 0.368 244 4.259 868.5 −17.0 0.200 2504.363 865 −17.5 0.188 162 2.827 883 −10.7 0.413 294.5 5.140 881 −16.60.209 22.39 0.391 882 −17.4 0.191 137 2.391 885 −16.22 0.218 22 0.384

The appropriate characteristics of the neutralizing signal can bedetermined by a formula in which the data to be transmitted is inputinto the formula or by a lookup table in which the data to betransmitted is used.

Phase Filtering

If information signal in the data wave is phase modulated, phasefiltering is useful in the receiver for demodulation Phase modulation isparticularly valuable for incoming signals that have noise andinterference from nearby data channels. In one example, it is assumedthat the incoming signal has the desired data in the signal but the dataportion of the signal is obscured by noise and interference in thesignal. To perform the phase filtering, an assumption of the value(e.g., a 1 or a 0) of the data is made and a signal equivalent to thatassumption is injected into the incoming signal. If the assumption ofthe data value is correct, constructive interference between theincoming signal and the injected signal will provide constructiveinterference and verify the assumption. If the assumption of the datavalue is wrong, destructive interference will show the assumption to bewrong. If the incoming signal and the injected signal are in a resonant(or “tuned”) circuit, the difference in the output signal between acorrect and incorrect assumption will be quite substantial. This isbecause the correct assumption on the injected signal and the incomingdata portion of the data signal will increase the output signal'samplitude every wave.

In one embodiment 1500 shown in FIG. 32, the incoming signal may besplit 1505 into 2 circuits wherein one circuit 1501 assumes that thedata is a “1” and the other circuit 1502 assumes the data is a “0”. Thesignal generators 1503 and 1504 generate signals equivalent to theirrespective assumption of 1 and 0 respectively. Resistors 1506 are usedto add the input signal to the simulated signals. If all four of theresistors shown are the same value, the signals will all be addedevenly. If gain is required for specific signals, the resistors ofdifferent values can be used. The output from these two circuits may berun through a signal comparison device 1507 and the output of the signalcomparison device provides a signal with a strong indication of whichassumption (“0” or “1”) is the correct assumption. While this outputsignal will be significantly different than normal wireless signals tobe demodulated, it can be analyzed with well known techniques usingstandard circuitry or digital signal processors (DSP).

It should be noted that while hardware circuits are shown throughoutthis disclosure to illustrate how specific signals can be generated,these signals and the functions of the hardware can be synthesizedthrough a variety of means which include but are not limited to: digitalsignal synthesis, waveform generator, arbitrary waveform generator,signal generator, function generator, digital pattern generator,frequency generator, frequency synthesis, direct digital synthesis, etc.For the purpose of this disclosure, all these terms and various hardwaresolutions are all synonymous and are to be within the scope of thisdisclosure.

While the foregoing has been with reference to a particular embodimentof the invention, it will be appreciated by those skilled in the artthat changes in this embodiment may be made without departing from theprinciples and spirit of the invention, the scope of which is defined bythe appended claims.

The invention claimed is:
 1. A communications apparatus, comprising: atransmitter that is capable of transmitting a channel across atransmission line; a carrier wave source that provides a carrier wavehaving a frequency to the transmitter; and a circuit that changes acharacteristic of the carrier wave to cause a substantial reduction inthe average power at the frequency of the carrier wave; wherein thecircuit that changes a characteristic of the carrier wave furthercomprises a neutralizing signal generator that injects a neutralizingsignal having a characteristic into the transmission line thatneutralizes one or more sidebands at one or more sideband frequencies ofthe carrier wave wherein the neutralizing signal destructivelyinterferes with the one or more sidebands at one or more sidebandfrequencies.
 2. The apparatus of claim 1, wherein the characteristic ofthe carrier wave further comprises a phase of the carrier wave andwherein the circuit that changes a characteristic of the carrier wavefurther comprises a circuit that shifts the phase of the carrier wave insuch a manner that there is a substantial reduction in the average powerat the carrier frequency.
 3. The apparatus of claim 1, wherein thecharacteristic of the neutralizing signal is determined by a formula inwhich the data to be transmitted is input into the formula.
 4. Theapparatus of claim 1, wherein the characteristic of the neutralizingsignal is determined by a lookup table in which the data to betransmitted is used.
 5. The apparatus of claim 1, wherein thecharacteristic of the carrier wave is selected from a group consistingof a phase of the carrier wave, an amplitude of the carrier wave and afrequency of the carrier wave.
 6. The apparatus of claim 1, wherein thecircuit that changes the characteristic of the carrier wave furthercomprises a modulator.
 7. A communications method, comprising: providinga carrier wave having a frequency; electronically changing acharacteristic of the carrier wave to cause a substantial reduction inthe average power at the frequency of the carrier wave; and injecting aneutralizing signal having a characteristic into the transmission linethat neutralizes one or more sidebands at one or more sidebandfrequencies of the carrier wave wherein the neutralizing signaldestructively interferes with the one or more sidebands at one or moresideband frequencies.
 8. The method of claim 7, wherein changing thecharacteristic of the carrier wave further comprises shifting the phaseof the carrier wave in such a manner that there is a substantialreduction in the average power at the carrier frequency.
 9. Acommunications apparatus, comprising: a transmitter that is capable oftransmitting data across a transmission line using a generated signal;and a circuit that adjusts the generated signal to minimize bandwidth ofthe signal; and a neutralizing signal generator that injects aneutralizing signal having a characteristic into the transmission linethat neutralizes one or more sidebands at one or more sidebandfrequencies of the carrier wave wherein the neutralizing signaldestructively interferes with the one or more sidebands at one or moresideband frequencies.
 10. The apparatus of claim 9, wherein the circuitadjusts the signal for one or more of a given carrier wave frequency, adata set, a data modulation method, a data rate, an amplitude and aphase.
 11. The apparatus of claim 9, wherein the circuit generates asignal that is out of phase with the signal to adjust the signal. 12.The apparatus of claim 9, wherein the circuit generates a signal that isout of phase with the sidebands of the signal to neutralize thesidebands.
 13. The apparatus of claim 9, wherein the timing of the phaseshifting of the signal prevents it from interfering with other channels.14. The apparatus of claim 9, wherein the transmitter further comprisesa lookup table that is used in the creation of the generated signal.